Overheating? - Common Reasons Pontiac can overheat

Cooling has long been an issue in performance enhanced gasoline combustion engines. We recommend engine temperatures not in excess of 180-200 degrees (F). The cooling system in your Pontiac engine is very simple consisting of only a pump, thermostat, fan, and radiator. Failure of only one of the components in the cooling system will result in excessive engine temperatures. Excessive engine temperature can damage an engine in mere seconds. Since different metals expand at different rates with increased temperature you can be sure that engine component clearances are altered, causing wear or premature failure. The most harmful effect of high engine temperature is detonation. Detonation for even a short period of time could damage your rod bearings or possibly even puncture the top of a piston. When attempting to resolve an issue with the cooling system one might start with a checklist covering these basic subjects and then we will move on to the more complicated ones:

Basic Cooling Checklist:

  • Is there a sufficient amount of coolant in the cooling system?
  • Is the thermostat stuck or needs replaced?
  • Is the radiator clogged? (Inside and out)
  • Is the radiator sufficient for the application?
  • Is there a fan shroud on the radiator?
  • Is the fan close enough to the fan shroud?

Pontiac Specific Checklist:

  • If the engine is freshly built were the proper gaskets used? (head & intake)
  • If the engine is 1969 or later are the plate and sleeves installed in the timing cover?
  • If the engine is 1969 or later are there good o-rings in the sleeves inserted in the timing cover?
  • If the engine is pre 1969 are both plates installed behind the water pump?
  • Is the impeller of the pump as close as possible to the plate behind it?

These checks can help you find faulty things that cause overheating. 

Possible Solutions

Advanced Checklist

  • Compression Ratio/Fuels
    • Many Pontiac engines came from the factory at 10:1 - 10.5:1 compression ratio. While this worked in those days because of higher grade fuels and availability of higher octanes, it is not the case for todays fuel. Example; Regular gas in the 1960's was 88-90 octane and high grade gas reached upwards of 100 octane. This is much higher than fuels today. We recommend no higher than 9.0:1-9.5:1 with cast iron heads and 10.0:1-10.5:1 for aluminum heads to stay pump gas friendly for todays fuels (91-93 octane). 
      • One easy way to see if your fuel or compression ratio is a culprit is to log temperatures on your normal fuel, run a tank of race fuel (100+ octane) and see if there is a difference in the operating temperature. If it is, contact us on ways you can reduce your compression ratio. If in the build process we can assist in piston face type (dish cc) and head upgrades with proper cc and/or milling. If assembled engine we can suggest multi-layered gaskets to help add overall chamber volume.
  • Timing
    • Improper timing can lead to inefficient combustion, causing the engine to generate more heat than normal
  • Is the air/fuel mixture of the engine too lean?

Possible Solutions

  • Upgrade to Multi-layered head gaskets (standard thickness is .040, can upgrade to .051-.120 thick) 
  • Upgrade to Aluminum Heads for better heat dissipation. Aluminum heads allow compression to be up to 1 point higher than cast iron (72cc cast iron at 10.5 is high compression typically requiring mixed fuel, 72cc aluminum head at 10.5 is pump gas compression)
  • Replace pistons with dished pistons. Cutting a dish into the top of pistons add overall volume to the cylinder. (requires rebalancing of the crank)
  • Change engine timing

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